1. Field of the Invention
The present invention relates to a dielectric ceramic containing a barium titanate based compound as its main constituent, and a laminated ceramic capacitor using the dielectric ceramic.
2. Description of the Related Art
As ceramic materials for use in laminated ceramic capacitors, barium titanate based compounds which have a high dielectric constant have been widely known. In addition, inexpensive base metal materials such as Ni, which have favorable conductivity, have been widely used as internal electrode materials.
Furthermore, in connection with the development of electronics technology in recent years, a reduction in laminated ceramic capacitor size and than increase in capacitance has rapidly advanced.
This type of ceramic capacitor has a ceramic sintered body obtained by alternately staking dielectric layers composed of a dielectric ceramic and internal electrodes, and applying a firing treatment, and has external electrodes formed on both ends of the ceramic sintered body. Reducing the dielectric layer thickness and increasing the number of layers stacked allows for the reduction in size and the increase in capacitance for the laminated ceramic capacitors.
Furthermore, Japanese Patent Application Laid-Open No. 2006-282481 proposes a dielectric porcelain composition for laminated ceramic capacitors, which includes a main constituent containing a barium titanate and includes an oxide of Al, and has a plurality of dielectric grains in which the Al concentration decreased from the grain surfaces toward the inner parts of the grains.
In the case of Japanese Patent Application Laid-Open No. 2006-282481, the dielectric grains configured to have an Al concentration decreasing from the grain surfaces toward the inner parts of the grains improves the TC bias characteristics (temperature characteristics of capacitance in the case of applying a DC voltage) and the temperature dependence of insulation resistance IR while ensuring a high dielectric constant of 1000 or more and favorable temperature characteristics of capacitance.